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help, my front brakes locked up.

This is my only car. So i need to fix it asap. The front brakes locked up on me and can't drive the car. The only way i can get them unlocked is by releaving the pressure by loosening the brake line and letting the brake fluid out. But after a few hundred yards they start to drag pretty bad. Could it be a bad proportioning valve. Any tips/help is greatly appreciated.

Check your brake booster first. start your car and let it run for about 3 seconds. Pull the vacuum line that connects from the intake manifold to the black pumpkin behind the master cylinder. If your hear it sucking in air. It's still good.

Check your master cylinder. Depress your brake pedal and if it depressed and you feel something stopping it from hitting the floor. It's good.

just happened out of the blue. Got home parked it. Got up in the morning and the car wouldn't move. I was like WTF? and then i started checking it. For some reason the calipers won't release unless i let the brake fluid out.

LOL This is happening to lotsa supras. Mine does 4 wheel lock though. I'm still trying to figure out what's wrong with it. I'm thinking about just getting new Rotors and Brake Pads and go to the junk and try to find some 4Runner 4 piston calipers.

This is my only car. So i need to fix it asap. The front brakes locked up on me and can't drive the car. The only way i can get them unlocked is by releaving the pressure by loosening the brake line and letting the brake fluid out. But after a few hundred yards they start to drag pretty bad. Could it be a bad proportioning valve. Any tips/help is greatly appreciated.

do you feel anything wrong when you step on the brakes? does it feel normal?

Still have the same problem. I removed the master cylinder, proportion valve, calipers and some of the brake lines. There was sludge build up in the reservoir for the master. So i cleaned up and flushed all the lines. The caliper sliding bolts were fine. They had no resistance on them. The calipers came out and went in like any other caliper i have worked on. I also cleaned the master cylinder and also took it apart just to make sure it was clean and not clogged. After all this work i put everything back together and bled the entire system. Went for a ride and the problem is still there.

Someone mentioned to check the brake booster. Exactly how do i do this? I noticed after i turn the car off and disconnect the booster vacuum hose i hear nothing. I thought vacuum was supposed to be held in there?

Still have the same problem. I removed the master cylinder, proportion valve, calipers and some of the brake lines. There was sludge build up in the reservoir for the master. So i cleaned up and flushed all the lines. The caliper sliding bolts were fine. They had no resistance on them. The calipers came out and went in like any other caliper i have worked on. I also cleaned the master cylinder and also took it apart just to make sure it was clean and not clogged. After all this work i put everything back together and bled the entire system. Went for a ride and the problem is still there.

Someone mentioned to check the brake booster. Exactly how do i do this? I noticed after i turn the car off and disconnect the booster vacuum hose i hear nothing. I thought vacuum was supposed to be held in there?

Check a few posts above this one. If you hear nothing your brake booster is BAD AND DO NOT DRIVE IT! you are not getting any vacum and it is causing you to lock up. Change it ASAP!

Check Car-Parts.com. I checked there and they have a shit load of brake boosters in texas. The part int he list is listed as POWER BRAKE BOOSTER. Cheapest i found it for was 30 bucks. good luck

My first '88 did this on the front/right tire. It was the Brake Caliper.
For me, it would sieze up over say a 10 minute drive, till 1st gear and 5Krpm and you couldnt move. It would release itself when it cooled down, but still.

If it was me, I would be replacing the calipers myself, since thats what it was when this happened to me before.

I'm just going to go the auto salvage tomorrow and buy me the booster, calipers and non-abs lines with proportioning valve.

TaSe - thanks for the info. I will call them to see how much is the shipping.

Flea 420 - i was driving my car awhile ago and it was fine for awhile and then the car started draggin, so i pulled over and released the pressure from one of the lines coming of the abs modulator. Then it drove fine again.

Since i'm going to spend some money in some calipers, does anyone know what 4 piston calipers would be a good upgrade. (not the mkiv, since they will be hard to find at a wrecking yard.) I don't mind the extra work needed to make them work.

To check your brake booster, pop your hood and start your car. Shut it off after 3 or 4 seconds. Go to the vacuum like that connects from the intake manifold to your brake booster. It's about half an inch thick iirc. Pull that off, if you hear suction. It still works.

So i fixed my problem today. It was the master cylinder that wasn't letting the brake fluid return to the reservoir. I went to the salvage yard so i can get all the non-abs lines, proportioning valve and misc items to remove my abs. Then i found a cressida and decided to use the master cylinder from that car. The return hole from the cressida's master cylinder looked a little bigger than the one from the supra. Got home and proceded to remove all the abs items. Put the cressida master cylinder and bled the brakes. Went for a test drive and voila... calipers don't lock up anymore. Also picked up an 89+ climate control for $15.00.

i ran into the SAME problem about 4 years ago on my ex's car and i replaced/swapped or disassembled and cleaned virtually EVERYthing between the brake booster and rotors. completely removing the ABS unit alleviated the problem but i think the problem came back a few years later after some highway racing/brake boosting.

but the symptoms between her car and the O.P.'s car were identical; brakes not releasing the grip and dragging so much that the rotors began to over heat, burn the pads, built boost at steady road speed and overheated/boiled the coolant. shutting the car off and letting it sit for an hour or more temporarily fixed the problem but it would come back again.

flash forward to today; my car is doing it mildly. the calipers are dragging slightly. its enough to make the car rock as it rolls to a stop. when the calipers arent stuck or seized, the car will roll to a stop on its own without the jerk/rock and will begin to roll forward/back when on the slightest of grades. when the calipers are dragging, the car will hold itself still on these grades. i managed to drive about 15 miles without using my service brakes and only downshifting, slight e-brake and rolling to a stop/thru blinking lights and the pressure releived itself.

are we now saying a brake booster w/ faulty diaphragm is the culprit of dragging or seized calipers? i think my booster is faulty because if i pump the brakes, the pedal resistance increases and the idle increases (im map-based now) as if it has a vacuum leak. also, when i turn the car off, i do not have reserve vacuum assist; im 99% sure my booster is leaking.